Straight from the Mobil 1 website (
www.mobil1.com)
Concerning Mobil 1 mixed with conventional (dino) oil:
"Mobil 1 is compatible with conventional motor oil, should it be necessary to mix the two. The additive package in Mobil 1 has been specifically developed to work with its synthetic base fluids, so diluting Mobil 1 with conventional oil will reduce the superior performance characteristics of Mobil 1. While mixing conventional oil and Mobil 1 is acceptable, we do not recommend mixing different types of synthetic oils, since they may be composed of different synthetic base fluids. Change the oil and filter before changing from another synthetic oil to Mobil 1." As a sidenote - synthetic blends are synthetic and conventional oil blended together after all.
Concerning breaking in an engine with conventional oil first:
"The tighter tolerances and improved machining of today's engines have reduced the significance of the traditional engine break-in. Few manufacturers call for any special consideration. Since Mobil 1 is factory fill in Corvette, Viper, Porsche and other high-performance vehicles, engine break-in is obviously not an issue with current-generation vehicles.
If your engine is an older model that has been rebuilt, you may wish to follow the original engine break-in schedule. In this case, where you may be changing the oil after just a few hundred miles, you might want to use a conventional oil initially and switch to Mobil 1 once you have reached a mileage that permits longer oil drain intervals."
As for flushing engine before switching to Mobil 1:
"No special preparation is necessary when switching from conventional oil to Mobil 1. We do not recommend mixing different types of synthetic oil, as they may be composed of different types of synthetic base stocks. Change the oil and filter when changing from another synthetic oil to Mobil 1."
